Experimental investigation of loading rate effects on the shear capacity of reinforced concrete deep beams

Unlike slender RC beams, shear failure mechanism of RC deep beams is mainly governed by shear compression; a considerable amount of the load is carried by the compression struts of concrete. For this reason, when subjected to a long-term sustained load, the shear strength of RC deep beam could be reduced as the sustained load might have negative impacts on the compressive strength of concrete. The purpose of this study is to investigate the influence of sustained loads on the shear capacity of RC deep beams. In this experiment, different loading rates were chosen as an alternative method to clarify the effect of sustained loads. Two main different types of loading rate, a normal loading rate of 10 mm/hr and a very slow loading rate of 0.01 mm/hr, were applied. 100x320x1200 mm RC beams with a ratio of shear span to the effective depth a/d=1 were tested under two-point loading. The test results showed that under very slow loading rate, the ultimate shear capacity was moderately reduced.